Field
Determination of the position of devices may be useful in various communication systems. For example, wireless communication systems that support emergency services may benefit from being able to make a vertical position determination of user equipment (UE) and/or network elements within a building or in other indoor environments, such as caves.
Description of the Related Art
In a mobile environment, locating the user can be essential to deliver emergency and to deliver location based services. Global positioning system (GPS) has become a default mechanism to determine the location of systems. The accuracy and precisions of GPS may be adequate for outdoor environments. Now that more small cell base stations are getting deployed, indoor based location systems may need to be considered. Due to its operating frequency, GPS does not work with the same accuracy indoors. Existing systems, despite their complexity, suffer from multipath propagation and are limited to x and y axis information.
The Federal Communications Commission (FCC) has released a request to have indoor position systems. According to this request, providers would be required to provide horizontal location information within 50 meters of the caller for 67 percent of 911 calls placed from indoor environments within two years of the effective date of adoption of rules, and for 80 percent of indoor calls within five years. Horizontal position can refer to x and y axis position. Additionally, providers would be required to provide vertical location information within 3 meters of the caller for 67 percent of indoor 911 calls within three years, and for 80 percent of calls within five years. Vertical position can refer to z axis information.
There may be various reasons for wanting vertical position in addition to horizontal position. In a large building, emergency responders may need to know which floor a person is on, not just the horizontal location. While 10 meter accuracy horizontally can get a responder to within shouting distance horizontally, 10 meters is about 3 floors vertically. Even if the users are on an adjacent floor that is less than 5 to 10 meters, they may be unreachable by shouting. The construction of ceiling and separation can make such attempts difficult. Thus, an order of magnitude greater accuracy may be needed in the vertical dimension to put the responder within shouting distance.
Most conventional radio-based location technologies have poor geometry for providing the vertical position indoors, and consequently lack the accuracy to achieve a shouting distance level of accuracy. Indoors, GPS may not work with accuracy, due to characteristics such as multi-path.
Alternatives to GPS for indoor position systems typically use some form of local map, and superimpose the user's movements on the map. The map, however, only gives x and y axis direction and not z axis.